I can rub you can rub he can rub we can rub you can rub they can rub
V-ing form
I can be rubbing you can be rubbing he can be rubbing we can be rubbing you can be rubbing they can be rubbing
Perfect
I can have rubbed you can have rubbed he can have rubbed we can have rubbed you can have rubbed they can have rubbed
V-ing perfect
I can have been rubbing you can have been rubbing he can have been rubbing we can have been rubbing you can have been rubbing they can have been rubbing
Negation
Simple form
I cannot rub you cannot rub he cannot rub we cannot rub you cannot rub they cannot rub
V-ing form
I cannot be rubbing you cannot be rubbing he cannot be rubbing we cannot be rubbing you cannot be rubbing they cannot be rubbing
Perfect
I cannot have rubbed you cannot have rubbed he cannot have rubbed we cannot have rubbed you cannot have rubbed they cannot have rubbed
V-ing perfect
I cannot have been rubbing you cannot have been rubbing he cannot have been rubbing we cannot have been rubbing you cannot have been rubbing they cannot have been rubbing
Interrogative form
Simple form
can I rub? can you rub? can he rub? can we rub? can you rub? can they rub?
V-ing form
can I be rubbing? can you be rubbing? can he be rubbing? can we be rubbing? can you be rubbing? can they be rubbing?
Perfect
can I have rubbed? can you have rubbed? can he have rubbed? can we have rubbed? can you have rubbed? can they have rubbed?
V-ing perfect
can I have been rubbing? can you have been rubbing? can he have been rubbing? can we have been rubbing? can you have been rubbing? can they have been rubbing?
Interro-negative form
Simple form
can I not rub? can you not rub? can he not rub? can we not rub? can you not rub? can they not rub?
V-ing form
can I not be rubbing? can you not be rubbing? can he not be rubbing? can we not be rubbing? can you not be rubbing? can they not be rubbing?
Perfect
can I not have rubbed? can you not have rubbed? can he not have rubbed? can we not have rubbed? can you not have rubbed? can they not have rubbed?
V-ing perfect
can I not have been rubbing? can you not have been rubbing? can he not have been rubbing? can we not have been rubbing? can you not have been rubbing? can they not have been rubbing?